The World Health Organization in Europe called on Wednesday for measles vaccination campaigns to be stepped up across the region after recording 22,000 cases of the highly infectious disease since the start of 2014.

Saying she was "taken aback" by high case numbers, Zsuzsanna Jakab, the U.N. health agency's European director, said the 22,149 reported cases from seven countries threatened the region's goal of eliminating measles by the end of 2015.

Recent measles outbreaks in the United States and Brazil suggest that immunization rates in some areas have dropped below levels needed to prevent the spread of cases imported into the Americas, Pan American Health Organization/World Health Organization (PAHO/WHO) experts said today.

The US Centers for Disease Control and Prevention (CDC) today reported 19 more measles cases, most of them part of a large outbreak linked to Disneyland in California, lifting the national total to 121.

The disease was eliminated from the United States in 2000, and the resurgence of cases over the past few years—fueled by low vaccination rates in some communities—has stoked concerns that the virus could become endemic again.

In December, an outbreak of measles at Disneyland put a spotlight on the issue of vaccinations. According to the United States Centre for Disease Control (CDC) there were 644 cases of the measles from 27 states in 2014, the largest number of cases since it was thought to be eliminated in 2000.

As the Disneyland measles outbreak continues to spread, some are pointing the finger at Merck ($MRK), maker of the only U.S.-approved measles vaccine. But when it comes to encouraging the public to get vaccinated, there's a limit on how much the company can do, its R&D chief says.

AS THOMAS PEEBLES jabbed a needle into the arm of a sick student in 1954, he told him, “Young man, you are standing on the frontiers of science.” Indeed he was. Using blood collected at the boy’s school, Peebles was able to isolate the measles virus, which John Enders then used to craft a vaccine in 1963. That year there were around 400,000 cases of measles in America. In the decade to 2013 the average number of annual cases dropped below 100. The disease is no longer endemic in America (though it still kills thousands abroad).

The measles outbreak which started at Disneyland has grown to 96 confirmed cases in eight states, with California accounting for the vast majority.

At least nine new cases surfaced in recent days, including two in Arizona, where health officials worry that hundreds of people may have been exposed to the virus on the eve of the state hosting the Super Bowl.